This application claims priority to Japanese Patent Application No. 2002-59873, disclosure of which is incorporated herein by reference.
The present invention relates to a compressor for compressing a refrigerant in two stages (hereinafter referred to as a “two-stage compressor”) and to an automotive air conditioner using the two-stage compressor.
For example, Japanese Unexamined Patent Publication No. 2000-97177 (JP 2000-97177 A) discloses a compressor used in a refrigerating cycle. The compressor comprises a two-stage compression mechanism for compressing a refrigerant in two stages and an electric motor for driving the compression mechanism. By compressing the refrigerant in two stages, a compression ratio in each stage can be lowered as compared with single-stage compression. It is therefore possible to suppress refrigerant leakage in a compression process and to thereby improve the efficiency of the compressor.
However, the two-stage compression mechanism is driven by a single drive source comprising the electric motor, the electric motor must be large in scale. This results in an increase in production cost of the compressor.
In case where the compressor is used in an automotive air conditioner, the two-stage compression mechanism may be driven by an automobile engine. In this event, however, the operation of the two-stage compression mechanism depends upon the rotation speed of the engine. This may result in execution of excessive and useless compression work exceeding a desired cooling power, increasing the load upon the engine and lowering fuel economy.